Confession: I have no idea what “Millennial” means in terms of demographics. I assumed it was a catch-all for “teens,” or at the very least people much younger than I.

But I, according to comScore’s definition, am apparently a Millennial (18- to 34-year-olds, shockingly). And as a Millennial living in the United States, I swear no allegiance to any one social network.

That’s according to comScore’s latest marketing survey, which states that of the seven so-called major social networks, we Millennials aren’t locked in to one at the expense of others. (And “major” means Facebook, Twitter, Tumblr, Instagram, Pinterest, LinkedIn and Snapchat, per comScore.)

What’s most interesting here is where Facebook comes into play: Despite the rise of other competing social networks over the past decade, Facebook still hosts 91 percent of Millennials, nearly double that of the next closest network, Instagram at 46 percent (which, of course, Facebook also owns). From there, Twitter through LinkedIn all hover somewhere in the 30 percent to 40 percent signups range.

That makes the “Can Facebook stay cool forever?” narrative a bit more problematic. Instead of departing Facebook in droves for other, hotter newcomers, Millennials seem to be splitting their time among the networks, while using Facebook as a sort of a baseline — a lowest common denominator shared with other age groups, all the way to 55 and up.

Which is sort of how Facebook is positioning itself these days. Instead of being “cool,” Facebook wants to be “useful,” a utility and perhaps a gateway to the rest of the Web, via link distribution and app discovery.